1. Chapter 4 Computer Memory
EET Advanced Digital
Chapter 4
Computer Memory

2. Memory Primary and Secondary Storage Primary is part of main memory
at one point, DISK, DRUM, or CORE memory was used.
Secondary is an antiquated view of a system, but usually refers to mass storage.
Old technology included the use of punch card, tape or DISK/DRUM memory

3. Memory Main memory in modern PC’s uses a volatile type of memory
Semiconductor memory is the rule
Non-Volatile memory is used for special purpose functions within the PC
BIOS
CMOS - is battery backup version on non-volatile memory
EEPROM or FLASH memory

4. Measurement
Capacity of memory is based on the amount of digital information that can be stored.
Bits/ Bytes/ Nibbles
Words
Double Words
Quad Words
Line

5. Memory is used in modern based on GRANULARITY
the smallest amount of memory that can be addressed
Increased bus widths have INCREASED the size of the smallest granule accessed
Pentium/Pentium Pro use eight-byte modules

6. Technologies
Random Access Memory
Dynamic Memory
Data In
Data Out

7. Static Memory - referred to as SRAM Read Only Memory ROM
Mask ROM - older bios chips
PROM - Programmable
EPROM - Erasable Programmable ROM
EEPROM - Electrically Erasable PROM
Flash Memory

8. Where’s the Memory Memory uses in a PC L1 L2 C A H E C A H E
Main Memory
CPU
Mass Storage
Cache

9. Memory Use Storage of program information Storage of BOOT information
program and settings
Storage of DATA

10. Logical Organization Real Mode Memory - legacy of the 8086 processor
1 Mbyte address space
base memory

11. Logical Organization Protected Mode memory Lower Memory
Provides the entire address space of the processor
4 Gbytes +
Lower Memory
Legacy stuff again
< 640k - conventional DOS memory

12. BIOS Data Area Upper Memory Vector Table - lower 1k
the upper 384k of memory address space
top 32K - ROM Bios memory

13. High Memory Frame Buffer memory 64kB+16 bytes above Upper memory
address line A20 allows this
a function of binary round-off
Frame Buffer memory
Part of video memory

14. Shadow Memory
Provides solution to slower ROM memory providing BIOS functions.
ROM memory is slower than fast RAM for a variety of reasons - bus width, intrinsic speed, etc.
BIOS is ‘shadowed’ into RAM at boot time, allowing faster access to these functions.
Other ROM memory - controller cards, video, etc may be shadowed.

15. Cache Memory
provides the speed interface between slower memory/devices and the faster memory/devices

16. System Resource Memory
Memory allocated by ‘heaps’
older OS problems with release of memory on program exit.

17. Unified Memory Architecture
UMA
maps main memory into video display address space

18. Performance Memory Speed based on access speed of integrated circuits
-12 is 120 nS memory,
Must have faster memory than called for by processor speed.
Bus interface may be the problem.

19. Caching
Cache Size - 1k
256 k most favored
Note: Celeron processor suffered severe performance penalties by failing to include Cache memory

20. Cache Performance four sections
show cache hits for access to store a single line - one for each transfer
would be best

21. Cache Mapping Direct Mapped Full associative set-associative
CACHE mapped to block of memory
Full associative
CACHE can be for any block of memory
very costly - complex
set-associative
sections of CACHE are direct mapped.

22. Synchronous Burst Ram - SRAM (note acronym conflict)
Burst-Mode Caches
blocks of data at a time
Synchronous Burst Ram - SRAM (note acronym conflict)
Pipelined burst SRAM

23. Cache consistency
Write-through
Write-back

24. Memory Types Static Column Ram Page-Mode RAM (FP)
Extended Data Out Memory (EDO)
Burst EDO DRAM
Synchronous DRAM
Enhanced DRAM
Cached DRAM

25. Rambus DRAM
Multibank DRAM
PC100 RAM
PC166/266/333/400 etc.

26. Memory Packages
DIP
SIPP
SIMM
30 pin
72 pin
DIMM
168 pin

27. Assignment Complete Chapter on memory
Review ‘Tom’s Hardware Guide: Ram Guide.
Research ‘other’ RAM packages that may be available.